Many factory formed panels are used in the building industry by which a wall, roof, etc. is formed for a building. Systems employing modular units that are prefabricated to enable creation of a range of architecturally varied buildings are known. With all such panels and systems, efforts have been made to reduce input material costs, to improve fabrication techniques so as to reduce production costs, and to adapt the characteristics of the prefabricated elements to reduce on-site handling problems and make erection of buildings less dependent on skilled trades.